Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/03/20
Area Forecast Discussion
National Weather Service State College PA
1058 PM EST Mon Mar 2 2020
An upper level disturbance crossing Northern Virginia and
Maryland will bring some light rain to the southeast half of
Pennsylvania until shortly after midnight.
A weak cold front will stall out near the south shore of Lake
Erie overnight. An area of low pressure will then track north
across the state on Tuesday. A rapidly developing storm is
likely to develop off the east coast late in the week, but it
should remain too far east to significantly impact Pennsylvania.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A cloudy, relatively tranquil and mild evening was in progress
across the region.
A compact mid and upper shortwave drifting by just to the south
of the Mason-Dixon line was producing some very light rain
across the southern half of the CWA (likely just a few to
several hundredths of an inch). Hi res models show this rain
exiting the far southeast zones by shortly after midnight.
During the late night/early morning hours of Tuesday, any breaks
in the cloud cover will give brief shots of radiational cooling
and the already tight T/Td spreads (with sfc dewpoints in the
upper 30s to low 40s) will contract to a deg F or less under
light wind. Will mention areas of 2-3SM fog for the 04-13Z Tue
Min temps will be in the low to mid 40s in most spots, and
nearly steady in the upper 30s to around 40F over the Northern
Tier of PA.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Upper trough approaching from the northern plains will organize
a developing surface low along the stalled front over the Ohio
Valley overnight into Tuesday, then track northeast across Pa
during the daylight hours Tuesday. POPs got nearly categorical
as a result of a several hour period of rain Tuesday, before
large scale subsidence decreases activity again by Tuesday
RAP sfc based cape peaks at 700-900 j/kg across the southern
third-half of PA in the 19Z Tuesday - 01Z Wed window, and some
scattered TSRA embedded within the overall larger areas of SHRA
looks plausible based on strong dynamics/uvvel associated with
the left exit region of a howling 165 kt upper jet tracking east
from the lower-mid Ohio River Valley.
Highs Tuesday will still be mild ranging from upper 40s
north to mainly the upper 50s across the southeast (with a few
lower 60s sprinkled about).
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
A tight gradient in wake of departing low should create gusty
winds during this period. Bufkit soundings support 30-35kt gusts
during Wednesday. The air mass crossing the lakes shouldn`t be
cold enough to generate lake effect. However, a fast moving
shortwave could produce a few snow showers over the northwest
counties by late Wednesday.
Med range guidance supports fair weather Thursday, as surface
high pressure builds across the state. 00Z NAEFS and ECENS both
indicate late week coastal cyclogenesis will be too far east to
significantly affect central Pa. However, passage of upper
trough is likely to be accompanied by scattered rain/snow
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
TAFS updated several times this evening.
Conditions went downhill fast this evening.
Earlier discussion below.
00Z TAFS sent.
Airmass quite dry, thus conditions not real low as of early this
Light rain becomes rather spotty after midnight.
However, expect conditions to lower late tonight into Tuesday,
as a weak low pressure system lifts northeast along the cold
Improving conditions late Tuesday, as the cold front moves east
of the area.
Not clear cut on the weather for late Thursday night into
Friday. Will depend if the low over the Great Lakes can
interact with the the system forming near the east coast.
Tue...MVFR/IFR with periods of rain ending Tue night.
Wed...Low cigs and rain/snow showers possible NW 1/2.
Thu...No sig wx.
Fri...Restrictions possible with rain/snow.
Sat...No sig wx.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
558 PM CST Mon Mar 2 2020
.SHORT TERM...(This evening through Tuesday)
Issued at 109 PM CST Mon Mar 2 2020
Aloft: RAP tropopause analyses...WV imagery and aircraft obs
indicated an elongated trof extending from low pres over James Bay
acrs NEB to low pres over AZ. A separate shrtwv trof was in the
NW flow over SA/MT. The initial trof will move S and E of the CWA
before sunset. The upstream shrtwv trof will then move thru
tonight... introducing NW flow for tomorrow...within which there
will be a weaker shrtwv trof...but it is fcst to remain N of the
Surface: 1015 mb high pres was over KS. 991 mb low pres was over
cntrl Canada with a sfc trof extending S to the NEB panhandle. The
high will fill as it departs to the E tonight. Meanwhile...the
low will move E acrs Srn Canada. The associated sfc trof will
cross the CWA. Wk high pres will emerge into KS tomorrow...with a
wk low moving SE from AB to SD.
Rest of this afternoon: Variable clds...ranging from cldy to sunny
as there is a large patch of clds 6-7K ft moving E. Sun will
become more prevalent as these clds exit to the E. Clds are
holding temps down...but should see highs in the 40s...with a cpl
50-51F readings from Cambridge-Phillipsburg-Beloit.
Tonight: IR satellite shows an arc of multi-layered mid-high clds
preceding the aprchg shrtwv trof and currently moving into the
Panhandle. This band of clds will move thru tonight with clearing
from NW-SE behind it. Lows around 30F give or take a cpl degs.
Tue: Sunny and becoming brzy...espcly in the afternoon. Without
the wind...it would be warm. Highs 60-65F. Pls see fire wx section
.LONG TERM...(Tuesday night through Monday)
Issued at 109 PM CST Mon Mar 2 2020
Pattern: More of what we`ve seen since mid-Nov. Low-moderately
amplified W-E flow.
Aloft: NW flow from Tue will cont thru Fri. The flow will back a
little bit Wed into Wed night as a strengthening shrtwv trof
crosses the Nrn Plns. Heights will rise over the Plns Fri though
as an amplifying ridge approaches. Once the ridge passes Fri
night...SW flow will prevail Sun-Mon. A wk shrtwv trof is fcst to
move thru Sun night into Mon AM.
Surface: Wk high pres will depart NEB/KS Wed as a Clipper dives
to ND. The cool front associated with this low will move thru Wed
night. Strengthening high pres will gradually build in and crest
over the rgn Thu night. This high will gradually drift to the E
coast thru the wknd...with NEB/KS in the windy warm sector until
the next cool front moves thru Sun night. Incrsg dwpts will help
minimize the fire danger...but it won`t eliminate it.
Temps: Continued mild. Lots of 50s and 60s until Mon...when the
warmth is suppressed and 40s appear N of Hwy 6. Sat and Sun will
be the warmest days. Would not be surprised to see some 70s Sat
and Sun. The blend of mdl 2m temps suggests widespread 70s is
Precip: Dry until Sun night. The 06Z/12Z GFS both suggest a few
shwrs Sun afternoon. The 00Z and 12Z EC suggests it will remain
dry until after the passage of the cool front. If something should
develop along the cool front...some rumbles of thunder could occur
in weak instability. The EC will probably be right as 2 days of SW
flow will advect an EML over the rgn.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 554 PM CST Mon Mar 2 2020
After a brief MVFR ceiling in KGRI during the first hour, we
should have VFR conditions for the rest of the forecast. Gusty
wind should decrease quickly as the sun sets, and will probably be
on the gusty side once again for Wednesday late morning into
Issued at 109 PM CST Mon Mar 2 2020
Fire wx conds should be near-critical Tue and possibly Thu
afternoons. Tue N of I-80...and espcly N of NEB Hwy 92. Thu
confidence is low as winds will be highest where RH`s will be more
marginal (25-30%)...and that will be E of Hwy 281. We need some
time to refine the RH fcst and where the risk of near-critical
might be...if it even occurs.
Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
919 PM EST Mon Mar 2 2020
A cold front will stall out over the Ohio Valley through tonight.
A wave of low pressure will track along the front Tuesday,
pushing it southeast through the area by Tuesday night. High
pressure will return for Wednesday and Thursday before a cold
front moves through early Friday. Low pressure will likely
intensify well to our northeast late in the week.
.NEAR TERM /THROUGH TUESDAY NIGHT/...
A shortwave-trough is currently moving through the fcst area
this evening with a dry slot evident on water vapor images over
srn WV and southwest VA. Showers currently moving through the
area will last another 2 to 4 hrs before exiting east of the
area around midnight. Rainfall will be generally light less than
a tenth of an inch. Clearing will take place overnight as
shortwave-ridge builds overhead by daybreak Tue.
A second stronger upper air disturbance is expected to move in
late Tue night with another round of showers moving into the
Appalachians shortly after daybreak and reaching the metro areas
by Noon time. Could be multiple rounds of showers tomorrow
before trough axis crosses the area late Tue night and dries
things out finally by Wed.
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
A cold front will remain stalled over the Ohio Valley Tuesday with
high pressure over the Atlantic. A southerly flow will continue to
usher in mild conditions during this time, but there will be a
couple disturbances that pass through in the west to southwest flow
aloft. The first disturbance will pass through during the morning
and midday hours, likely triggering some showers. There will be a
break in the precipitation along with some sunshine behind the
disturbance during the afternoon. However, a second disturbance will
pass through the area late in the day into the early evening hours.
This disturbance will also be accompanied by the frontal passage,
and the flow will strengthen aloft due to a a digging shortwave over
the Great Lakes. In fact, the upper-level trough may swing toward a
negative tilt during this time.
The sunshine and southerly flow ahead of the front may provide some
instability. Most guidance is showing around 250-500 J/KG of SBCAPE.
Some guidance is higher like the HRRR and some guidance is a bit
lower like the NAM12 (due to more cloud cover). Therefore,
confidence in the instability is low at this time. However, with the
strengthening dynamics and frontal passage, scattered showers and
perhaps even some thunderstorms are possible during this time. If
there are higher amounts of instability are realized, then
thunderstorms may be capable of producing gusty winds and/or hail.
Drier conditions are expected behind the cold front overnight
Tuesday as westerly winds take over.
High pressure will build overhead for Wednesday and Wednesday night,
bringing dry and more seasonable conditions. Confidence has
increased that low pressure will be suppressed to the south.
.LONG TERM /THURSDAY THROUGH MONDAY/...
An amplified split flow pattern will be in place Thursday morning
over the continental United States. In the northern stream, a potent
shortwave trough (near the Aleutian Islands as of Monday morning)
will dive southeastward toward the Great Lakes. Meanwhile, a
southern stream shortwave trough (the sheared remnants of a cutoff
mid/upper-level low moving onshore of southern California as of
Monday morning) will be in the process of ejecting across the lower
Mississippi River Valley toward the Tennessee River Valley. Model
guidance has been having trouble resolving the potential interaction
between these two waves in separate streams at the end of the week,
but there is a broad consensus that the streams will phase and
strong surface low pressure will develop offshore well to our east.
Even with the eventual parent surface low a few hundred miles away
tracking northeastward over the northwestern Atlantic Ocean, clouds
and precipitation with the mid/upper trough in the northern stream
seem plausible. Precipitation type is likely to be mainly rain east
of the mountains given warm conditions prior to the system moving
in, with a changeover to snow showers most likely over the Allegheny
Highlands by nightfall Friday. Several Canadian, GFS and European
ensemble members phase the low a bit sooner, with a few even phasing
soon enough to draw in cold air and change (heavier) precipitation
to snow east of the mountains. However, this appears unlikely given
the progressive nature of the pattern and lack of downstream
blocking (evidence by a positive AO/NAO and negative PNA).
In summary, this system bears close watching given the strong
dynamics and potential, but overall the risk of significant
widespread winter weather (or other hazardous precipitation such as
heavy rain) seems unlikely at this time.
What seems more likely is gusty northwesterly winds in the wake of
departing low pressure as high pressure of Arctic origins noses its
way toward our region from the Upper Midwest next weekend. Colder
than normal temperatures combined with the wind will make it feel
more like mid-winter than early March, which is ironic since it`s
been consistently mild basically all winter up to this point.
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
A disturbance will likely bring some showers for a few hour
period this evening. MVFR conditions are possible during this
time. VFR conditions will return behind the disturbance, but
there may be patchy fog overnight. Confidence in the fog at this
time is low due to high and mid-level clouds along with light
Another disturbance will bring the likelihood for showers later
Tuesday morning through midday, and MVFR conditions are possible
during this time. A cold front will pass through late Tuesday
afternoon into Tuesday evening. A shower or thunderstorm may
accompany the frontal passage. Gusty winds/hail cannot be ruled out,
but the threat appears isolated at this time. Dry conditions will
return overnight Tuesday behind the cold front. High pressure will
control the weather for Wednesday and Wednesday night.
Sub-VFR is possible as low pressure passes the area late in the week
(mainly Friday). Gusty northwesterly winds likely follow Friday
night into Saturday.
Winds should diminish some overnight into Tuesday as the
gradient subsides. Winds should remain below SCA criteria most
of the time, but it may be close for a period overnight and
again Tuesday afternoon. A cold front will pass through the
waters Tuesday evening. A shower or thunderstorm may accompany
the frontal passage. Locally gusty winds or hail cannot be ruled
out, but confidence is low at this time.
A westerly flow is expected behind the cold front overnight Tuesday
and Wednesday, before winds turn northwest ahead of high pressure
Wednesday night. An SCA may be needed for portions of the waters
during this time.
The pressure gradient will likely be pretty weak Thursday into
Friday as the local area is expected to be sandwich between low
pressure systems. As those two lows consolidate to one and deepen
rapidly out at sea, the pressure gradient will increase markedly
heading into the weekend. Gusty northwesterly winds are likely
Friday night into the weekend as high pressure builds in, with gale
MARINE...Small Craft Advisory until midnight EST tonight for ANZ530>543.
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
609 PM CST Mon Mar 2 2020
00Z issuance...VFR conditions at the beginning of the period will
be followed by ceilings lowering to MVFR along with IFR conditions
in fog possible near the coast. MVFR ceilings are expected to
continue through Tuesday. Patches of rain will increase in
coverage over interior areas overnight while a cold front
approaches from the north. Rain coverage continues to increase
over much of the area on Tuesday as the front advances slowly into
the area. Southerly winds at 5 to 10 knots continue overnight then
increase to 5 to 15 knots and become southwesterly Tuesday
morning, then diminish later in the afternoon. /29
.NEAR TERM UPDATE /Now Through Tuesday night/...Closed upper low
near the northern area Baja tonight continues slowly eastward
into western Texas through Tuesday night while an upper trof over
the northern and central Plains advances into the interior
eastern states. A frontal boundary currently located from near the
ArkLaTex to the Ohio River valley advances southward and moves
slowly through the forecast area to near the coast Tuesday
afternoon into Tuesday night. A series of shortwaves meanwhile
continue to move across the region, which when combined with the
frontal boundary moving into the area along with abundant deep
layer moisture (precipitable water values near 1.5 inches) will
support a trend towards categorical pops for much of the period
from Tuesday into Tuesday night. MLCAPE values remain low through
mid morning on Tuesday (150 J/kg or less) then increase modestly
to 200-450 J/kg through mid Tuesday afternoon. 0-1 km Helicity
values increase to 200-300 m2/s2 overnight, but an examination of
model soundings shows that the meager instability is located
mainly well aloft (above ~ 700 mb) and it`s also likely that the
convection will not be surface based. Based on this, the potential
for strong or severe storm development overnight looks rather
low. Shear values trend much lower during the day on Tuesday (0-1
km Helicity generally less than 50 m2/s2) so the potential for
strong to severe storm development remains rather low. Indicated
shear values increase significantly Tuesday night, but model
soundings show that convection will rather likely be elevated (and
rooted near 900-850 mb), and becomes increasingly elevated as the
frontal boundary advances to near the coast late in the night.
That said, will need to continue to monitor this pattern. A moist
southerly flow continues during the period, which will likely
result in fog developing over the bays and near shore waters with
visibilities potentially dropping to near 1 nm. A Marine Dense Fog
Advisory is in effect from late this evening through Tuesday
evening as a result. A High Risk of rip currents remains in effect
as a persistent onshore flow leads to a gradual increase in
onshore swell. /29
.PREV DISCUSSION... /issued 353 PM CST Mon Mar 2 2020/
NEAR TERM UPDATE /Now Through Tuesday night/...Closed upper low
off the California coast translates eastward over the northern
Baja tonight continuing eastward over the northern Mexican border
Tuesday. Downstream of this feature a fairly zonal flow pattern
remains in place over the southeastern states within which a
series of mid- level impulses move across the region. A surface
front sinks southeast across the OH River Valley to the Ark-La-
Tex by daybreak Tuesday. Ahead of the front, physical model
solutions indicate a moderately strong 40KT H85 jet streak lifting
quickly east northeast Tuesday morning over the interior and
coupled with Wet-Bulb Zero (wbz) heights as low as ~ 10.5kft
suggest a small hail threat in any morning convection. The latest
SREF and high resolution HRRR also indicates potential for 200 to
300 M2/S2 of 0-1 KM helicity evolving over the northwest zones by
and after 3 AM tonight sliding eastward along and north of US HWY
84 through late Tuesday morning which could support the potential
for a few rotating storm updrafts and perhaps a tornado threat. A
marginal risk of severe weather is outlooked over the interior. A
light to moderate moist southerly flow continues over the area and
there is a signal supporting fog formation late this evening and
overnight. Fog could be locally dense, especially closer to bays
and sounds. A gradual increase in deep layer moisture will also be
occurring. Precipitable water values lift up to between 1.3 to
1.6 inches by late tonight into Tuesday afternoon and with forced
ascent better with southeastward progression of boundary, PoPs to
increase from north to south. The front continues southeast,
becoming quasi-stationary draped west to east very near the
central Gulf coast Tuesday night into Wednesday morning. During
this time frame, the better 0-1 km warm sector MUCape extends
along and south of I-10 to out over the Gulf waters, so there is
some question as to the poleward severe weather threat Tuesday
night north of the boundary with any convection looking to become
more elevated in nature, perhaps a (hail threat) if it does occur.
Latest 12Z assessment of wbz`s are not overly impressive by
daybreak (12Z Wednesday) with values mostly 11 to 12 kft.
Temperatures to be well above seasonal normal.
A High Risk of rip currents remains in effect as a persistent
onshore flow leads to a gradual increase in onshore swell. /10
SHORT TERM /Wednesday and Wednesday night/...The middle part
of this week still appears on track to be very wet with an excessive
rainfall potential as well as a chance for some strong to severe
thunderstorms depending on just how the developing weather event
takes shape. The models are still in pretty good agreement with the
track and timing of the upper closed low pressure area as it moves
out of old Mexico early Wednesday morning, east across Texas and
Louisiana late in the day and overnight, then approaching the
Mississippi River by late Wednesday night (around 12Z Thursday),
although the EURO weakens the feature a little more than does the
Differences are still evident with the surface low pressure
area and downstream warm front, although models do seem to be
getting a little better in agreement here too. By midday Wednesday
the EURO develops a surface low over interior southeastern Texas,
while the GFS is along the southeast Texas coast near Houston.
Models somewhat similar in moving the low east across Louisiana
through Wednesday night and into our western most forecast area
(southeast Mississippi) by the end of the night. The question is how
far does the associated warm front make it inland across our area.
As of now, it appears that the EURO brings the warm front a little
further inland over our area, with the warm sector bringing a little
more instability to the coastal portions of our forecast area. This
could bring a chance for strong to severe thunderstorms, primarily
along the coast and just inland (in the vicinity of the warm
front)Wednesday night. SPC currently has this area outlooked with a
SLIGHT RISK for severe storms, which seems prudent.
The potential for additional excessive rainfall looks to be the
biggest threat during the short term period. With the warm frontal
boundary set up in the general vicinity of our forecast area. This
has the potential to be a heavy rainfall event, and WPC has our
entire area outlooked with a SLIGHT RISK of Excessive rainfall.
PWAT`s are expected to be in the 1.7 to 1.9 inch range late
Wednesday through Wednesday night. We have slightly bumped up our
rainfall total across the area, now expecting a possibly 3 to 5
inches across much of the area (especially eastern two thirds), with
localized amounts of 5 to 7 inches. The ground remains saturated and
many rivers at bankfull or above flood stage (mostly in minor flood
threat levels at this time). This additional rainfall could easily
increase the threat of flash flooding and could bring any rivers
that are still in Minor flooding back into the Moderate flood
category. We will monitor for need of Flash Flood Watch for portions
of our forecast area, coming with later forecast packages. /12
EXTENDED TERM /Thursday Through Monday/...Mid/Upper level shortwave
will be weakening and ejecting east across the Tennessee Valley
region on Thursday as a surface low located just to the west of our
forecast area early in the day shifts quickly east, being situated
more or less over our area by midday Thursday and then weakening and
moving east of the area by the end of the day Thursday. Some
lingering showers and thunderstorms expected during the first half
of the day Thursday, but rain chances lowering later in the day.
Thereafter, a dry forecast is then expected for most of the extended
period as high pressure ridging shifts east across the area. Next
chance for precipitation will be at the very end of the extended
period as return flow begins to bring more low/mid level moisture
back into the region. Daytime highs on Thursday near normal (around
70 give or take a few degrees) for this time of the year, dropping
into the low to mid 60s Friday and Saturday as the high moves across
the area, then rebounding back to around normal by Sunday and
Monday. Nighttime lows Thursday night ranging from low/mid 40s
interior to around 50 at the coast. Cooler again Friday and Saturday
nights with lows in the mid to upper 30s inland to the lower 40s at
the coast, and then back into the 40s and 50s again Sunday night and
in the mid to upper 50s areawide by Monday night. /12
MARINE...Surface high pressure over the southeast states breaks
down as a cold front approaches from the northwest Tuesday. Widespread
fog, locally dense at times, is expected late this evening and may
continue through Tuesday night. Visibilities likely to be reduced to
less than a mile will increase hazardous navigation of all marine
craft and ocean going vessels. Winds to strengthen midweek as a
surface low approaches from the west. The low will bring unsettled
weather and perhaps a few strong thunderstorms Wednesday into
Wednesday night. The low will then push east, with moderate to
strong offshore flow resulting in building seas late in the week. /10
AL...High Rip Current Risk through Thursday afternoon for ALZ265-266.
FL...High Rip Current Risk through Thursday afternoon for FLZ202-204-
GM...Dense Fog Advisory from 9 PM this evening to midnight CST
Tuesday night for GMZ630>636-650-655.
This product is also available on the web at:
Area Forecast Discussion
National Weather Service Marquette MI
546 PM EST Mon Mar 2 2020
.SHORT TERM...(This evening through Tuesday)
Issued at 348 PM EST MON MAR 2 2020
Mid-afternoon clearing under weak high pressure ridging has brought
relaxing winds, climbing temperatures, and overall pleasant Upper
Michigan afternoon and evening. RAP analysis shows our next
advertised shortwave currently north of the Dakotas. This wave is
progged to move east tonight, reaching western Lake Superior around
06Z tonight. Increasing SW flow ahead of this trof will bring a
period of WAA/isentropic ascent that will assist in -SN to increase
from west to east after 06Z. Snow will then increase slightly as the
trof axis swings through and additional synoptic forcing pivots
through the cwa after 12Z. Although the precip will be generally
light, models show decent agreement in amounts and timing...although
the RAP and NMM remain a little further ahead of the other models.
With better forcing expected a little later, expecting a little
higher totals across the east than the west. Snow amounts across the
west will remain near a half an inch to an inch, with an inch to an
inch and a half across the east by tomorrow evening.
With clearing skies and a period of calmer winds ahead of the next
shortwave, may see temps fall into the upper teens tonight, but
otherwise expecting low to mid 20s. Expecting temps to fall off
initially before remaining steady, or perhaps increasing towards the
tail end of tonight. Tomorrow, temps will rebound with gusty winds
expected behind the trof as the boundary layer destabilizes with
some weak CAA along with it. Could see some gusts as high as 30 to
35 mph at times, especially west and in the higher terrain.
.LONG TERM...(Tuesday night through Monday)
Issued at 450 PM EST MON MAR 2 2020
Models suggest that a progressive pattern will prevail through the
weekend. A shortwave trough will move out of the area Tuesday night
with a period of quiet weather Wednesday before another more
vigorous shrtwv moves through the region Thursday into Thu night.
Mid level ridging with another warmup is expected by next weekend.
Tuesday night, Expect some light wnw flow lake effect/enhanced snow
with favorable 850-700 moisture and inversions around 8k ft even
with 850 mb temps only to around -10C. However, any accumulations
should be light, generally less than inch.
Wednesday, any leftover light lake effect snow will diminish or end
early. Surface ridging and drier air moving into the area will bring
at least partial clearing, allowing temps to climb into the mid to
Wednesday night through Thursday, the models, especially the ECMWF
and GEM, have trended farther south with the path of the shrtwv and
associated sfc low compared to the GFS/GEFS. Regardless of the path,
a period of WAA/isentropic lift snow ahead of the low will likely
give way to diminishing pcpn in the afternoon. However, as the
shrtwv digs to the south and strong cyclonic northerly low level
flow develops, a period of moderate to heavy lake enhanced snow is
likely Thursday night. There is low confidence on the snow amounts
given the fast moving system and lingering uncertainty with the
shrtwv location. Confidence is also low with pcpn type/timing as
temps may not climb high enough to support rain if the track ends up
south of Upper Michigan. In addition, very gusty winds to 30-35 mph
are also likely with strong the strong pres rise and tight gradient
forecast behind the low. This could result in very poor vsby near
Lake Superior along with some beach erosion.
Fri-Mon, leftover snow Fri morning will end by afternoon as sfc
ridging again quickly builds into the region. Mid level ridging and
strong WAA along with a decent amount of sunshine will push temps to
the upper 30s and lower 40s Sat and at least into the mid 40s to
around 50 Sun. The next shrtwv and front is likely to near or move
through the area by Mon bringing a chance of rain changing to snow.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 545 PM EST MON MAR 2 2020
VFR conditions will continue overnight until some light snow with a
system moves through Tue morning. Conditions will fall to MVFR Tue
morning with the light snow moving through at all sites. Will even
go to IFR at SAW Tue morning in the snow.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 348 PM EST MON MAR 2 2020
Winds throughout the week will continue to bounce up and down as a
series of low pressure systems and troughs pass across northern Lake
Superior or just north into Ontario. As a trough and associated cold
front pass across the lake tomorrow, winds shift west to northwest
to 30 knots with a few gale force gusts to 35 knots possible.
Ridging builds back over the area again Wed into Wed allowing winds
to briefly diminish. A third trough passes over the lake on Thursday
and there could be a period of north gales 35-40 knots behind this
system late Thu night into Fri morning.
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
1006 PM EST Mon Mar 2 2020
Seeing a break in the precipitation across the forecast area this
evening. Due to this, went ahead and decreased the Pops for the
remainder of the evening and the early overnight period. The
shortwave trough from early today has now lifted out into the Mid-
Atlantic with another shortwave trough currently across West
TN/KY. Radar imagery indicates severe storms associated with this
shortwave trough to the west. At 300 mb, there is a strong 140-150
kt jet that stretches from Southern Plaints eastward into the
Tennessee River Valley. The best forcing with this jet is still
located to the north and west of the area. Winds at 850 mb are
responding to this divergence aloft with a broad 40-50 kt low
level jet currently located to the north and west. This low-level
jet will move into the forecast area in the 09-12z timeframe. The
0-1 km SRH values will increase responding low-level jet into the
250-400 m2/s2 range. The main limiting factor for severe storms
will be the instability. The timing of the system really limits
the SBCAPE values with storms moving in just before daybreak.
Additionally, most model soundings suggest an inversion just above
the surface keeping storms elevated. However, just above this
inversion lapse rates are impressive in the 7-8 degree C/km range.
Overall, storms will be moving into a more stable atmosphere as
they progress to the east. Based on the impressive lapse rates
above the inversion and shear values cannot rule out a few strong
to marginally severe storms with damaging wind gusts and
marginally severe sized hail being the main threats. Storms will
sweep through the area near daybreak with drier conditions
forecast by Tuesday afternoon.
00Z TAF DISCUSSION.
IFR to VFR conditions to start the TAF period with the first
round of precipitation exiting to the east. IFR conditions
currently at CHA will continue over the next several hours before
the next round of showers/storms approach from the west.
Widespread showers/storms are forecast overnight into early
Tuesday morning ahead of a frontal boundary starting in the 09-15z
timeframe. There is enough elevated instability to include VCTS
at CHA and TYS. Conditions will improve quickly to VFR as the
precipitation exits to the east late in the TAF cycle.
/ISSUED 316 PM EST Mon Mar 2 2020/
SHORT TERM (This Evening through Tuesday)...
First jet streak/wave is moving out of the area with the
isentropic lift and jet forcing exiting the region early this
evening. The low-level jet will weaken by 7 PM ET this evening.
Cove Mountain observation still shows strong wind gusts between
50-60 mph thus will continue the wind advisory for the Smoky
Mountains until 6 PM.
A break in the rainfall until around midnight then another
stronger upper jet around 140kts will move across the Tennessee
valley. From around Midnight through 9 AM ET, fairly strong upper
forcing due to the jet moves back into the area. Models show the
low-level jet pulling moist/warmer air into the boundary layer
with some cooling in the mid-levels. Result will be increasing
instability, mainly elevated, early Tuesday morning. Look at SPC
Outlook and HREF shows some fairly strong convective complex
moving into the area. Some bowing features noted on the HRRR
reflectivity which will tap into the increasing low-level jet to
produce isolated strong to possibly damaging wind.
Also, the mid-level cooling will increase the lapse rates and hail
CAPES. The stronger storms could produce small hail up to 1/2
inch. The greatest risk is the Plateau, western section of the
central valley, and southwest Tennessee. The latest HRRR suggest
the southern Plateau and southeast Tennessee (CHA) have the
For Tuesday, after early morning convection the convection will
diminish. However, a frontal boundary will drift slowly east which
will likely produce scattered convection over the eastern areas in
The increasing low-level jet by early Tuesday morning may warrant
another wind advisory for the Smoky Mountains.
LONG TERM...(Tuesday night through Sunday night)...
The extended period begins with a southern stream of energy across
northern Mexico with a departing shortwave across the Ohio valley.
As the shortwave continues to eject east, precipitation will come to
an end Tuesday night with mainly dry weather expected on Wednesday
as high pressure to the northwest advects a dry airmass southward.
Models continue to show a southern trend regarding the placement of
the front with the 00Z and 12Z ECMWF showing hardly any QPF across
the forecast area. The 12Z GFS shows much of the same until
differences begin to present itself on Thursday. The quicker GFS
begins to phase this southern stream with a northern stream impulse
as early as Thursday while the slower ECMWF keeps this southern
stream much further south and weaker. PoPs will increase on Thursday
as this upper level impulse moves through or near the area.
Temperatures near normal to start the extended period off will drop
to below normal values toward the end of this week.
The weekend features northwest flow aloft, with precipitation
possible in the higher terrain as 700-500mb flow begins to ramp up
in magnitude. Cold air advection will create cooler conditions with
temperatures running near average for the weekend period. Some of
the higher peaks could see a very brief change over to snow, but at
this point am not anticipating accumulations. A strong ridge builds
in to close the weekend period out with dry weather expected into
the beginning of next week. Temperatures are expected to begin
moderating to near and above normal values.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 53 69 47 59 46 / 60 80 20 30 60
Knoxville McGhee Tyson Airport, TN 51 65 42 60 44 / 70 90 20 20 50
Oak Ridge, TN 50 66 41 62 43 / 80 90 20 10 40
Tri Cities Airport, TN 47 62 37 59 39 / 70 70 30 10 20
Area Forecast Discussion
National Weather Service Spokane WA
637 PM PST Mon Mar 2 2020
The next few days will be breezy to locally windy. Periods of
light to moderate snow will impact the mountain passes at times
but dry weather is expected across Basin. Precipitation chances
expand to the lower elevations toward next weekend, potentially
including a bit of snow if the timing is right.
Made a minor update to the gridded forecast to mention patchy
blowing dust around the Moses Lake area this evening where Dodson
Road web cams show some dust getting picked up by the 35-40 MPH
wind gusts. Given the isolated nature of the stronger gusts no
major impacts are expected at this time, but will continue to
00Z TAFS: An upper jet to the north will continue to place the
region on the stable side of the jet with strong westerly flow
continuing to favor turbulent conditions in the lee of the
Cascades. For tonight model soundings favor LLWS for KEAT as well
as KPUW with winds aloft decreasing Tuesday morning for the
removal of LLWS. Although surface winds and gust will gradually
increase Tuesday with the approach of a cold front. Regarding
CIGS, VFR conditions will continue across Central WA and Lewiston
area due to downslope flow off area mountains. Meanwhile over NE
WA/Idaho Panhandle models shows an expansion of MVFR stratus
overnight into Tuesday morning. JW
.PREV DISCUSSION... /issued 349 PM PST Mon Mar 2 2020/
Tonight through Wednesday: The next couple of days will feature a
moderately strong Polar Jet that will sag slowly out of southern
British Columbia (BC) over the Northwest. There are two
discernible shortwave disturbances that water vapor satellite
imagery reveals in the northwest flow. The first is moving onshore
into BC this afternoon. Dynamics will largely remain north of the
region with lift primarily going to be supplied by orographics.
Some weak lift will occur along a warm front, but generally this
will only result in increasing mid to high level clouds over the
basin. Radar shows precipitation increasing on the windward slopes
of the Cascades this afternoon. It`s snowing up at Stevens Pass,
but web cams show wet roads with a surface temperature of 33
degrees. Some slushy light snow accumulations will be possible up
at this pass through the evening. Lookout Pass will also see
accumulating snow beginning later in the evening between about 900
PM and 200 AM according to the latest HRRR model run. Expect
winter travel over the pass with between 1 to 3 inches of snow
Winds will also need to be monitored overnight into Tuesday
morning. The position of the upper level jet is favorable for
breaking mountain waves in the lee of the Cascades. Sounding
profiles and cross section analysis supports a stable layer right
at mountain top level indicating the potential for mountain waves
to become trapped and potentially mix down to the surface. Winds
aloft are not anticipated to be strong enough for damaging wind
gusts and confidence of these stronger winds aloft actually mixing
down is low. It`s possible for some advisory level wind gusts
between 40-50 mph mixing down onto higher benches above the
Wenatchee Area and onto the Waterville Plateau, but this looks to
be isolated enough that a wind advisory is not needed.
The second shortwave disturbance is out at 50N/160W in the Gulf of
Alaska. Water vapor satellite shows a stronger dry slot behind the
front, which indicates a more dynamical wave than this first one
for tonight. Timing for this next one will be Tuesday night into
Wednesday morning. Impacts will be similar with a slightly higher
magnitude compared to tonight: snow amounts will range from 3 to
6 inches at Stevens Pass a 1 to 3 inches at Lookout Pass, as well
as breezy to windy conditions. Coverage of winds will be greater
with breezy to windy conditions across much of the region. The
upper level jet will be directly over the region by this time, but
weaken a bit to around 110 kts at 250 mbs. Models don`t show a
stable layer across the Cascades like tonight, so that will be
different. Winds at the surface will be strongest early Wednesday
with speeds up to 50 kts at 850 mbs from Wenatchee to Spokane.
The timing is not good for mixing, but there will be some cold air
advection with the front that will help mix down at least a
fraction of these stronger winds. I don`t see a high potential
for those 50 kt winds mixing all the way down to the surface, but
40 to 45 mph gusts will be possible. Wind advisories may be need
for the Wednesday morning to early afternoon period, but just not
enough confidence at this time. /SVH
Wednesday night to Monday: the Inland Northwest sees one
system exit, before a more amplified pattern develops with broader
precipitation chances. First Wednesday night to Thursday a mid-
level ridge builds in ahead of the deepening offshore trough, The
flow turns from west-north to southwest as a warm front lifts in.
Look for limited snow chances around the Cascades Wednesday night
to early Thursday, increasing late Thursday as some deeper
moisture nudges in ahead of offshore trough. Elsewhere look for
some middle to high clouds. Thursday night into Saturday the long-
wave trough makes its way inland, with an increase in
precipitation chances. The best risk initially remains in the
mountains, before expanding across the lower elevations of eastern
third of WA and ID going into Saturday. The lee of the Cascades
and deeper Columbia Basin overall has a limited precipitation
Precipitation type looks like mostly valley rain and mountain
snow. However near the Cascade valleys a rain/snow mix or at at
times all snow is possible. The best risk for all snow will be in
the night/early morning hours. Other snow may mix into the lower
elevations during the night/early morning hours. The first threat
will be around the northern valleys Friday and then over a broader
area late Friday into Saturday. Some instability may be found
Saturday afternoon, which may lead to some graupel or snow showers
mixed in as well. There is some threat some light accumulation
could occur in the lower elevations across eastern WA/ID but
confidence is low. Secondary upper disturbances move in between
Saturday night and Monday, with cooler air and the continuation of
the unstable lapse rates. This will keep the threat of light
rain/snow showers away from the lee of the Cascades and deeper
Columbia Basin, with the risk shifting more to just the Panhandle
mountains by Monday. Precipitation would be a rain/snow mix, with
more snow than rain during the night/early morning hours again.
.PRELIMINARY POINT TEMPS/POPS...
Spokane 38 54 37 49 30 55 / 10 0 0 10 0 10
Coeur d`Alene 36 52 37 47 29 54 / 30 0 20 30 0 10
Pullman 38 52 38 47 32 56 / 30 0 20 30 0 0
Lewiston 41 60 43 54 36 63 / 20 0 10 10 0 0
Colville 32 54 32 50 26 52 / 20 0 0 10 0 10
Sandpoint 35 48 35 44 26 48 / 40 10 20 60 0 20
Kellogg 34 44 35 41 28 50 / 70 20 50 70 10 10
Moses Lake 41 61 36 55 31 56 / 0 0 0 0 0 0
Wenatchee 39 58 35 50 31 52 / 10 0 10 10 0 10
Omak 33 56 32 48 29 49 / 10 0 0 0 0 10